1. Field of the Invention
The present invention relates to a sealing structure for sealing three-surface mating portions of a connecting portion. of a first member, a second member and a third member which is provided so as to extend over the first and second members by allowing a plate gasket to beheld between the first and second members and also allowing a liquid packing to be interposed not only between the first member and second member but also between the first and second members and the third member.
2. Description of the Related Art
The applicant of the present invention has already proposed a sealing structure for sealing three-surface mating portions of a connecting portion of three members by a combination of a plate gasket and a liquid packing (JP-A11-230356).
In the proposed sealing structure, a reservoir portion for a liquid packing having a depth greater than the thickness of a plate gasket and a relatively large capacity is formed between gasket mounting surfaces of a first member (a cylinder block) and a second member (a cylinder head) which are adapted to hold the plate gasket therebetween so that a part of a liquid packing for providing sealing between the first and second members and a third member (a chain case) is filled in this reservoir portion as well, whereby it is ensured that the aforesaid sealing is properly provided even if there exists an error in size the plate gasket.
It has been found, however, that the above proposed sealing structure causes the following drawbacks due to the presence of the reservoir portion for the liquid packing:
1. The setting speed of the liquid packing filled in the reservoir portion having the relatively large capacity is slower than that of the liquid packing filled. in the other portion, whereby a waiting time becomes longer before sealing properties inspection (pressure inspection) work is started, this deteriorating the working properties;
2. The amount of the liquid packing used becomes large; and
3. The reservoir portion for the liquid packing adversely affects the rigidity of the three-surface mating portions.
The present invention was made in view of the aforesaid situation, and an object thereof is to provide a novel sealing structure which can solve the problems.
With a view to attaining the above object, according to the aspect of the invention, there is provided a sealing structure wherein a plate gasket is held between gasket mounting surfaces of a first member and a second member and wherein a liquid packing is interposed between packing surfaces of the first and second members and a packing surface of a third member adapted to be provided on the first and second members so as to extend thereover, whereby three-surface mating portions at a connecting portion of the first, second and third. members are sealed with the plate gasket and the liquid packing, the sealing structure being characterized. In that at the three-surface mating portion, the gasket mounting surfaces of the first and second members which confront each other across the plate gasket are both formed flat and also both formed in such a manner that the gasket mounting surfaces extend longer. than an end edge of the plate gasket toward the packing surface of the third member and expand wider than the plate gasket inwardly thereof, and that a gap having a depth equal to the thickness of the plate gasket is formed between the gasket mounting surfaces of the first and second members in such a manner that the gap extends around from the end edge side of the plate gasket to an inner edge side thereof, whereby a part of the liquid packing for providing sealing between the packing surfaces of the first and second members and the packing surface of the third member is filled in the gap.
According to the construction, the three-surface mating portions at the connecting portion of the first, second and third members can securely be sealed with the plate gasket and liquid packing, and in particular since the packing filled between the gasket mounting surfaces of the first and second members which confront each other across the plate gasket can only be filled up to the depth which is equal to the thickness of the plate gasket, the setting speed of the liquid packing so filled can be increased, as a result of which the waiting time before the inspection of the sealing properties of the liquid packing can be reduced, whereby the working properties of the inspection work can greatly improved. On top of this, the amount of liquid packing used can be reduced. Moreover, there is no need to form a recessed portion in the gasket mounting surfaces of the first and second members, respectively for storing therein liquid packing. Furthermore, being attributable to increase in area of the mating surfaces of the connecting portion of the three members, the connecting portion of the three members is formed thick, and this increases the rigidity of the connecting portion and reduces the flexure of the mating surfaces of the connecting portion, thereby making it possible to attempt at improving further the sealing properties of the connecting portion. In addition, since the thickness of the liquid packing at the three-surface mating portions of the connecting portion of the first, second and third members can be made to coincide with the thickness of the plate gasket, there is no likelihood that the sealing function of a product such as an internal combustion engine scatters product by product.